This invention relates to multi-stage reformed-gas generators (fuel converters) in general, and more particularly to an improved type of multi-stage reformed-gas generator.
A gas generator of this general type is disclosed in U.S. application Ser. No. 372,422 filed June 21, 1973 and assigned to the same assignee as the present invention. As disclosed therein, a reformed-gas generator of this nature is useful for the operation of internal combustion engines. It comprises essentially two reaction chambers, each containing a catalyst with the reaction chambers connected for series flow. Between the reaction chambers, means for feeding in a gas serving as an oxygen carrier is provided. As disclosed therein, the second reaction chamber may be followed by further reaction chambers with a gas serving as an oxygen carrier fed into the flow between subsequent chambers.
A reformed-gas generator of this nature is capable of converting liquid, hydrocarbon fuels which are low in harmful substances, i.e., fuels containing no additives such as lead or cyclic hydrocarbons and which have a low sulfur content, into a gas mixture containing methane, carbon monoxide and/or hydrogen. In order to obtain a sootless conversion, this fuel low in harmful substances is evaporated and after evaporation mixed with a gas serving as an oxygen carrier which is at least partially made up of quantities of exhaust gas fed back from the internal combustion engine and/or other gases such as air serving as oxygen carriers. The mixture obtained is then conducted over the catalyst at elevated temperatures. The gas mixture (reaction gas) obtained by conversion at the catalyst is then fed, after a further amount of gas serving as an oxygen carrier is mixed therewith to the internal combustion engine and burned therein. In the operation of an internal combustion engine using such a reformed gas generator, the content of harmful substances found in the exhaust gas is substantially reduced.
In the specific embodiment disclosed in the above identified application, the reaction chambers each contain one or more catalyst carriers which are preferably in the form of highly porous, perforated sintered blocks, each in turn containing catalyst. These sintered blocks are provided with a large number of passage holes arranged approximately parallel to each other and in the direction of flow of the gases flowing through the generator. In the disclosed embodiment, the gases serving as oxygen carriers are fed to the mixture between the reaction chambers using separate mixing chambers which are arranged between and separate the reaction chambers. Specifically, the evaporated fuel is mixed with a gas serving as an oxygen carrier, such as air and/or fed-back exhaust gases, in a mixing chamber ahead of the first reaction chamber and then fed into that chamber. To the gas mixture leaving the first reaction chamber, which will comprise reformed gas and components of unreacted fuel vapor, additional gas serving as an oxygen carrier is added in a further mixing chamber after which the gas mixture with additional oxygen is fed to a second reaction chamber where the fuel components which have not yet been reacted are converted.
Although this type of generator works well, the perforated sintered blocks used as catalyst carriers have a relatively high specific gravity and are relatively expensive to manufacture. Thus, there is a need for a multi-stage reformed-gas generator of this general type, in which the catalyst material has a lower specific gravity than that of perforated sintered blocks and is at the same time less expensive to manufacture while still maintaining the necessary reaction capabilities. Furthermore, the gas generator described in the above identified application is somewhat bulky and thus, an improved gas generator which is more compact is desirable.